This invention relates generally which includes, among other things, a subsea wellhead housing installed at the ocean floor, a tubing hanger installed in the wellhead housing having a bore above the tubing hanger for suspending the tubing string and a flapper valve installed either in the tubing hanger or below the tubing hanger for hydraulically controlling flow through the tubing hanger or into the tubing hanger.
During the completion of an offshore well, the tubing hangers are typically lowered into supported positions within the wellhead housing through a blowout preventer (BOP) stack installed above the housing. Then, following completion of the well, the BOP stack is replaced by a Christmas tree having suitable valves for controlling the production of well fluids, connecting the tubing hanger to the Christmas tree on one end, and the annulus of the well on the other end.
In most versions of the tree assembly, the tubing hanger has a bore with sealing means, so that the tubing hanger has a fluid barrier between the annulus and the passageway in the tubing hanger. However, during completion of the well, as well as after completion of the well, there may be reasons to communicate between the tubing hanger bore and the annulus to permit fluid circulation between them. The present invention relates to a sealing means that can be installed in a tubing hanger or below a tubing hanging to open and close the tubing hanger passageway.
Subsea tubing hangers having valves for sealing off the passageway of the tubing hanger are shown, for example, in U.S. Pat. Nos. 3,360,048, 4,335,526 and 4,449,583 as well as in U.S. Pat. Nos. 5,687,794, 5,143,158, 5,044,432 and 4,333,526. In most of the patents, however, as well as in other apparatus of this type, the passageways through the tubing hangers are typically controlled by valves which have sealing parts of elastomeric material which may be damaged by extreme heat or other deleterious conditions of the well fluids.
Also, in the valves of certain of these patents, movement of the valves from closed to open positions requires the installation and manipulation of a separate tool which is cumbersome and subject to breaking and not hydraulic manipulation. Furthermore, in most situations, the valves are moved from closed to open positions by springs, which are highly susceptible to malfunction.
None of the valves disclosed appears to focus on the safety aspects of controlling fluid flow through use of a flapper safety valve.
An object of this invention is to provide a safety valve, and in particular a flapper valve in a tubing hanger or below a tubing hanger, which is hydraulically operable for controlling the passageway to minimize the possibility of leakage past the fluid barrier provided by the hanger.
An object of the invention is to provide a safety valve, which is so reliable and inexpensive to install, that the valve assembly has significant environmental advantages, and lower construction costs.
A further object of the invention is to provide a flapper valve either integral in the tubing hanger or below the tubing hanger, which can be operated in a reliable manner, without requiring an additional tool.
The invention comprises a wellhead housing having a wellhead bore disposed therethrough and at least one casing hanger supported within the wellhead bore for suspending at least one casing string within the well head bore. The invention further comprises a tubing hanger having a tubing hanger passageway adapted to be supported in the bore of a subsea wellhead. The invention includes a flapper valve disposed in the tubing hanger passageway and adapted for opening and closing the tubing hanger. The flapper valve comprises a flapper valve body having a flapper valve closure member substantially in the form of a sealing segment, which can be a concave spherical segment. This sealing segment defines an annular valve seat concentric with the tubing hanger bore. A flapper member is most preferably a planar member, such as a plate which is disposed in the passageway, or in sealing engagement with the passageway, and is capable of rotatable movement from a valve position in which the flapper member is removed from the annular valve seat forming an open valve position to a closed valve position in which the flapper member extends transversely across the flow passage forming a sealing engagement with the annular valve seat. The flapper member further comprises a sealing surface substantially in the form of a convex spherical segment, wherein the convex spherical segment is disposed intermediate between first and second planar surfaces of the valve.
For use in a subsea wellhead having an annulus, further including a wellhead housing having a wellhead bore therethrough and at least one casing hanger supported within the wellhead bore for suspending at least one casing string within the well head bore, apparatus comprising: a tubing hanger including a tubing hanger body having a fluid passageway disposed therethrough connected to an annulus; a flapper valve disposed outside of said tubing hanger in said annulus adapted for opening the fluid passageway in said tubing hanger, said flapper valve having a housing connecting said valve to said tubing hanger, a flapper valve closure member substantially in the form of a segment defining an annular valve seat concentric with said tubing for said flapper valve; a flapper member disposed in said valve chamber for rotatable movement from a valve position in which said flapper plate is removed from said annular valve seat to a valve position in which said flapper member extends transversely across said flow passage and forms a sealing engagement with said annular valve seat thereby preventing flow through said fluid passageway; a sealing surface having a segment disposed intermediate between a first and a second planar surface; and means responsive to pressurized fluid for hydraulically moving the valve member, which is preferably the valve plate, from a closed position to an open position.
Additionally, the invention further comprises means responsive to pressurized fluid from a remote source for hydraulically moving the flapper valve member, such as the valve plate, from a closed position to an open position.